Electrical apparatus with vaporizable liquid coolant



Aug. 26, 1958- PAUL NARBUTOVSKIH 2,849,523

NOW BY JUDICIAL CHANGE OF NAME PAUL NARBUT ELECTRICAL APPARATUS WITH VAPORIZABLE LIQUID COOLANT Filed Aug. 16, 1952. 2 Sheets-Sheet l Fig.l.

l8 INVENTOZ PAUL NAQBUTOVsKIH e B )ucuclAl. CHANGE o NAME PM. NA eu WITNESSES:

1958 PAUL NARBUTOVSKIH 2,849,523

NOW BY JUDICIAL CHANGE OF NAME PAUL NARBUT ELECTRICAL APPARATUS WITH VAPORIZABLE LIQUID COOLANT Filed Aug. 16, 1952 2 Sheets-Sheet 2 Fig.3. l2

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PAUL. NAQEUTOVSKIH, Now 8/ Juoaoum. CHANGE. QF: N WITNESSES:

AUL NAQBUT awyyzw A United States Patent ELECTRICAL APPARATUS WITH vAPoRIZABLE LIQUID COOLANT Paul Narbutovskih, now by judicial change of name Paul Narbut, Sharpsville, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 16, 1952, Serial No. 304,729

7 Claims. Cl. 174-15 This invention relates generally to electrical apparatus and more particularly to apparatus provided in conjunction with the electrical apparatus cooperative to utilize a fluid dielectric for dissipating heat and providing an insulating atmosphere.

This application is a continuation-in-part of application Serial No. 103,332, now abandoned, filed July 7, 1949, by Paul Narbutovskih, and assigned to the same assignee as this invention.

An object of this invention is to provide, in an enclosed electrical apparatus, depending on fire and explosionproof gases for its insulation and relying on vaporization of a liquid coolant to dissipate heat developed in use, means for controlling the cooling and condensing of the evolved vapors to control the temperature of the electrical apparatus.

Another object of this invention is to provide an enclosed electrical apparatus having a plurality of cooling tubes connected preferably in series for progressively receiving vapors of a condensable insulating coolant therein to control the heat dissipated therefrom and thereby control the temperature of the electrical apparatus.

A further object of this invention is to provide an enclosed electrical apparatus having a vaporizable liquid coolant therein with a plurality of series connected vertical cooling tubes for progressively receiving evolved vapors from the casing to control the cooling thereof, the vertical tubes being connected at the bottom thereof by a common return to the casing, the common return having a liquid trap therein to prevent flow of vapors therethrough between the tubes and the casing.

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawing, in which,

Figure 1 is a diagrammatic view of a transformer illustrating one embodiment of the teachings of this invention.

Figures 2 and 3 are diagrammatic views of transformers illustrating other embodiments of this invention, and

Figure 4 is a diagrammatic view of a transformer illustrating still another embodiment of the teachings of this invention in which the cooling device comprises a single cooling tube.

Referring to Fig. l of the drawings this invention is illustrated by reference to a transformer comprising a sealed casing 12 within which is disposed a magnetic core 14 and electrical windings 16 associated therewith disposed to seat on the base of the casing. For the purpose of simplifying the drawing the leads to the windings 316 and the bushings normally carried by the top or cover of the casing 12 are not shown.

As illustrated, the bottom of the casing 12 is provided with a sump 18 in which there is disposed a supply 20 of vaporizable liquid coolant. The supply 20 of the liquid coolant is relatively small as compared to the size of the casing 12 being normally only in the sump 18 out of contact with the core 14 and the electrical windings 16.

As disclosed in the Hill Patent 2,561,738, the vaporiz able liquid coolant may comprise the liquid fluorinated organic compounds selected from the group consisting of hydrocarbons, hydrocarbon ethers and tertiary hydrocarbon amines in which at least half the hydrogen atoms have been substituted by at least one halogen selected from the group consisting'of chlorine and fluorine, and' of which at least half of the halogen is fluorine. The hydrocarbons and the hydrocarbon groups attached to oxygen or nitrogen atoms may be aliphatic, aromatic, cycloalipatic and alkaryl. Liquid perfluorocarbons, perfluorocarbon ethers and perfluorocarbon tertiary amines boiling between 50 C. and 225 C. have outstanding properties. Perha-locarbon compounds composed of only carbon and a halogen selected from at least one of the group consisting of chlorine and fluorine, of which fluorine comprises at least half the halogen atoms have been found to be satisfactory liquid coolants for the purpose of this invention.

' The vapors of the fluorinated organic compound referred to hereinbefore have outstanding electrical insulating properties. They are superior to practically all other gases in such electrical insulating characteristics as breakdown strength, dielectric strength, power factor and resistance to formation of corona under similar conditions of temperature and pressure. These compounds are outstanding in their stability to chemical and thermal breakdown being surpassed only by the permanent gases. The fluorinated compounds in the liquid state exert negligible, if any, solvent or deteriorating action on ordinary insulating materials and varnishes employed in the preparation of conventional electrical elements such as windings, cores and coils.

As examples of specific fluorinated organic compounds which may be utilized in practicing this invention either alone or in mixtures, reference may be had to the following list of fluorinated organic compounds:

Boiling Point, C. Perfiuorophenanthrane 205 Perfluorodibutyl ether Perfluorotriethyl amine 71 Perfluorotributyl amine 178 Perfluorodimethylcyclohexane 101 Perfluoromethylcyclohexane 76 Perfluoro-n-heptane 82 Perfluorotuene 102 Perfluorocyclic ether (C F O) 101 Perfluorocyclic ether (C F 0) 52 Monochlorotetrafluoro (trifluoromethyl) benzene 137 Dichlorotrifluoro (trifluoromethyl) benzene Trichlorodifiuoro (trifluoromethyl) benzene 207 Monochloropentadecafluoroheptane 96 2-chloro-1,4-bis(trifluoromethyl) benzene 148 2-chlorotrifluoromethylbenzene 150 Perfluorodiethylcyclohexane 148 Perfluoroethylcyclohexane 101 Perfluoropropylcyclohexane 123 Chlorononafiuorobis (trifluoromethyl) cyclohexane 129 Perfiuoronapthalane 140 Perfluoro-l-methylnapthalane 161 Perfluorodimethylnaphthalanes 177 to 179 Perfluoroindane 116 to 117 Perfiuorofluorane Perfluorobicyclo-(2.2.l) heptane (746 mm.) 70

The amines, and ethers may have dissimilar halogen substituted hydrocarbon groups present as, for example,

. 3 2:2 dichloro- 1,1,1 -"trifluoroethyl perfluorobutylether and perfluorodibutylethyl-amine. The freezing points of the above listed liquid compounds are below zero degrees centigrade, many being below --50 C., so that they can be safely employed, individually or in mixtures, under nearly'all ambientconditions to be expected in service.

As a typical compound for use in the present invention, perfluoromethylcyclohexane can be employed to advantage as it has a boiling point of 76.3 C., a heat vaporization of 22 calories per gram at the boiling point, a specific heat of 0.2 calories per gram, a density of 1.8 and a freezing point below '50 C.

It will, of course, be understood that mixtures of the fluorinated organic compounds can be employed where each of the compounds has a boiling point above 50 C. and below the temperature capable of being withstood by the insulation of the windings 16. As a practical application, thos'e fluorinated organic compounds having boiling points within-the range of 50 C. to 225 C. are to be preferred.

In order to apply the liquid coolant 20 to the electrical winding 16, -a pump 22 'is disposed for operation to withdraw the liquid coolant 20 from the sump 18, the pump 22 being connected as'by a conduit 24 to a suitable spray device 25 from which the liquid coolant is distributed in the form of a fine spray (not shown) over the core 14 and the windings 16. The liquid coolant when thus delivered distributes itself as a thin film (not shown) over-the electrical elements within the casing 12 and is caused to evaporate freely after the electrical components are hot, thereby cooling the core 14 and the electrical windings 16. Instead of the spray devices 25, it is, of course, understood that a-system of conduits (not shown) may be employed for directing the vaporizable liquid coolant to specific points on the windings 16 for applying a film of the coolant thereto toeffect the cooling.

In order to efl'iciently control the cooling of vapors evolved within the'casing 12, a cooling device 26is illustrated as beingconnected to the casing 12 for receiving the vapors. In this instance, the cooling device 26 comprises a plurality of vertical radiator devices 28, 30, 32 and 34, connected in series with each other, the first radiator device 28 of the series being connected at its bottom as by a conduit 40 to the casing 12 n'ear'the upper end thereof for receiving the vapors .therefrom. In order that the cooling effect of the cooling "device 26 shall be applied progressively to the vapors,'the radiator devices are connected as illustrated, the top ofradiator device 28 being connected as by means of a conduit 42 to the bottom of radiator device '30 whereas the top of the radiator device 30 is connectedfas by means of the conduit 44 to the bottom of radiator device32. Likewise, the top of the radiator 'device 32 is connected by a conduit 46 to the bottom of radiator device 34, the top of the latter being connected as by means of a breather 52 such as the well known U type which contains a displ'aceable liquid (not shown) therein to the atmosphere. In practice, the radiators 28, 30, 32 and '34 may be either a single tube or a radiator section formed'of a plurality of parallel paths or tubes depending upon the cooling capacity required. Likewise, while only four of the radiator devices are illustrated, itwill be understood that this number may be increased or decreased as required to function as described hereinafter. Thus, as the vapors flow from the casing 12, they first fill the radiator device 28 and then progressively flow through the successive radiator devices, until sufficient radiator surfaces are contacted by the vapors todissipate the heat therefrom to maintaina given temperature within the casing 12. Preferably the conduits'40, 42, 44 and .46 are of small diameter in order to reduce the volume of the downward path of the vapor to thereby limit the possible mixing of the vapor and gas or air therein.

As will be appreciated, the vapors of the liquid coolant contained' in the cooling device '26 wi11condense to a liquid when cooled sufficiently and flow to the bottom of the radiator-tubes. In order to return the condensed liquid to the sump 18 Within the casing 12, a common return conduit 54 is connected as by means of vertical conduits 56, 58, 60 and 62 to the lower end of the radiator devices 28, 30, 32 and 34 respectively. As illustrated, the common return conduit 54 may be inclined toward the 'sump 18 to facilitate drainage of the liquid coolant from the radiators to the sump.

Inpractice, the common return 54 is positioned at a level lower than the liquid level maintained in the sump 18 whereby liquid coolant is maintained in the common return conduit 54 at all times in order to provide aliquid lock between the bottoms of the radiator tubes forming the cooling device 26 and the casing 12 to prevent flow of the vapors from the-casing 12 directly to the bottoms of the tubes of the cooling device 26. If such a direct flow is permitted the functioning of the cooling devices 28, 30 and 32 will be disturbed. As can be readily seen, under this condition each of the radiator devices, such as'28, and its associated conduit 42, will be filled with a light 'non-condensable gas. The heavy vapors of fluorinated organic liquid coolant, in their passage from the casing12toward the breather '52 through the conduit 54, should this path be opened, will by-pass all of the cooling devices, instead of flowing through them, thus rendering the overall system ineffective.

In operation, as the electrical apparatus is energized and develops heat therein, the heat is extracted by the evaporation of the vaporizable liquid coolant applied thereto and the vapors evolved will tend to fill the casing 12. As the vapors contact the surfaces of the casing 12, heat is dissipated'from the vapors. If the surfaces of the casing 12 are insufiicient to dissipate the heat generated in the electrical device contained therein, the vapors will completely fill the casing 12 and flow to the cooling device 26.

As the vapors of the liquid coolant tend to fill the casing 12, they force air or other gases contained therein into the radiator tubes or devices of the cooling device 26 so as to purge the casing 12. As the vapors tend to fill radiator device or tube 28, the air is forced ahead of the vapors into the series connected radiator tubes, the excess of the air or other gases contained in the tubes escaping to the atmosphere through the breather 52. In practice, if the combined surface of the casing 12 and the radiator section 28 is not sufiicient to dissipate the heat generated in the device, the vapors then flow progressively to the series connected tubes 30, 32 and 34 until suificient surface area of the radiator tubes is contacted to establish a'balance between the generated and the dissipated heat.

It will be noted that in the above arrangement, advantage is taken of the fact that the vapor of the coolant employed has a high density as compared to air, the ratio of the vapor to air density being equal to 10 or higher. For this reason, since the vapor is admitted into each of the radiator devices or tubes at the lower end thereof, there will be a relatively sharp line separating the'hot vapor from the cool air within the particular radiator device or tube in which the vapor terminates under a given load condition.

By connecting a suflicient number of the radiator tubes in series as described herein, it is found that a given temperature may be maintained in the electrical apparatus within the casing 12 while at the same time minimizing escape of the vapors from the system to the atmosphere. Thus when utilizing the apparatus of Fig. 1 sufiicient radiator devices will be connected in series so that the vapors under any abnormal operating condition of the electrical apparatus will progressively fill all, except, say the last one radiator tube or section connected in series, to dissipate sufficient heat to maintain the temperature required. On the other hand, as the load conditions change whereby'the heat generated in 'the electrical apparatus is reduced, the vapors in the radiator devices or tubes condense and less tubes are required to effect the dissipation of heat from the vapors to maintain the given temperature. Under such conditions, the breather 52 will permit air to enter the series connected radiator tubes or sections to fill the space therein as the vapors recede toward the casing 12.

By utilizing the cooling device as described, it is possible to pipe the breather 52 to any location away from the transformer or to connect the cooling device 26 at a remote point away from the casing 12, whereby the casing 12 may be buried or installed in hot and unventilated locations.

Referring to Figs. 1, 2, 3 and 4 of the drawings, like components illustrated in these figures have been given the same reference characters. Referring in particular to Fig. 2 of the drawings, there is illustrated another embodiment of this invention. The main distinction between the apparatus of Figs. 1 and 2 is that in the apparatus illustrated in Fig. 2 a different type of liquid trap is provided for preventing the direct flow of the vaporized liquid coolant from the casing 12 to the bottom portion of the radiator devices 28, 30, 32 and 34. In order to accomplish these functions, a substantially horizontal or slightly inclined common return conduit 70, having a plurality of U-shaped portions 80, 82, 84 and 86, is connected adjacent the lower portion of the casing 12 in communication with the interior of the casing 12, the conduit 70 being disposed to receive the condensed vapor from the radiator devices 28, 30, 32 and 34 through conduits 72, 74, 76, and 78, respectively. As illustrated, the U- shaped portions 80, 82, 84 and 86 are disposed below the level of the horizontal portion of the conduit 70. Such being the case, when the vaporized coolant condenses within the radiator devices 28, 30, 32 and 34 and flows downward into the conduit 70, the condensed vapor will accumulate in the U-shaped portions 80, 82, 84 and 86 to thereby prevent the direct flow of the vaporized coolant from within the casing 12 through the conduit 70 to the bottom portion of the radiator devices 28, 30, 32 and 34. Once the condensed vapor in the conduit 70 rises to the level of the horizontal portion of the conduit 70, the condensed vapor will flow into the casing 12 and will return to the sump 18 where it will be utilized for further cooling processes.

Referring to Fig. 3 there is illustrated still another embodiment of the teachings of this invention. In this embodiment still another type of liquid trap associated with the casing 12 and with the bottom portion of the radiator devices 28, 30, 32 and 34 is provided. In particular a substantially horizontal or slightly inclined common return conduit 90 having a turned-up portion 92 is provided. As illustrated the turned-up portion 92 of the conduit 90 is connected to the lower portion of the casing 12 and is in communication with the interior of the casing 12 in order to return the condensed vapor formed within the radiator devices 28, 30, 32 and 34 to the casing 12. The lower portions of these radiator devices are connected to the conduit 90 through conduits 94, 96, 98 and 100, respectively.

By providing the conduit 90 with a turned-up portion 92, the condensed vapor that flows from the cooling units 23, 30, 32 and 34 down into the conduit 90 is prevented from leaving the conduit 90 until the condensed vapor rises in the conduits 94, 96, 90 and 100 to the level of the upper portion of the turned-up portion 92 of the conduit 90. Therefore, the condensed vapor within the conduit 90 functions so as to prevent any direct flow of the vaporized coolant within the casing 12 to the lower portion of the radiator devices 23, 30, 32 and 34 through the conduit 90.

Referring to Fig. 4 of the drawings there is illustrated a further embodiment of this invention in which a larger cooling device 102 in the form of a radiator is substituted for the radiator devices 28, 30, 32 and 34 illustrated in Fig. 1. In order to permit the flow of the gas and vaporized liquid coolant from the casing 12 to within the cooling device 102, where the vaporized coolant is condensed, the upper end of a conduit 104 is connected to the casing 12 so as to be in communication with the interior of this casing at its upper end. The lower end of the conduit 104 is connected to a conduit 106, the upper end of which is disposed to receive the condensed coolant from the cooling device 102. For the purpose of returning the condensed coolant to the sump 18, a return conduit 105 is connected to the lower end of the conduit 106, the other end of the return conduit being connected to the sump 18 and in communication with the interior thereof.

When utilizing the single cooling device 102, unless it is fan or water cooled, the upper portion thereof operates at a higher temperature than the upper portion of the radiator device 34, of Fig. 1. The reason for this is that when the vaporized coolant enters the bottom portion of the interior of the cooling device 102, it heats it up. This heating is, to some extent, communicated to the upper portion of the cooling device 102, partly by conduction of heat along the metal walls, and partly by the upward convection currents of the cooling air outside of the cooler, if the cooling is accomplished by natural convection. As a result of this higher temperature in the upper portion of the cooling device 102, a greater loss of the vaporized coolant may be expected through the breather 52 in the embodiment of Fig. 4, as compared to the embodiments illustrated in Figs. 1 through 3, because, according to the well known law, the vapor content of the out-breathed gas is higher at a higher temperature.

The apparatus illustrated in Figs. 1 through 4 is selfpurging of air and other gases while minimizing the escape of the fluorinated organic vapors and insuring the return of the condensed liquid coolant from the cooling device to the casing 12. At the same time, the apparatus described permits operation at nearly atmospheric pressure within the casing 12 at all times. The apparatus will, also, operate within a predetermined range of deviation from the atmospheric pressure depending upon the characteristics of the breathing device 52. As will be understood, the heat dissipation from the surfaces of the casing 12 and the cooling devices 26 and 102 may be so proportioned as to maintain, even at the minimum load condition, a substantially pure vapor atmosphere within the casing 12. This latter condition is desirable when the dielectric properties of the vapor are depended upon for providing electrical insulation between parts of the electrical device enclosed within the casing 12.

While this invention has been described with particular reference to transformers, it will be understood that the invention may be applied to other types of electrical apparatus, such as, for example, switchgears, capacitors, generators, reactors, and the like. The application of the liquid coolant to the electrical device may be accomplished in a number of different ways to effectively obtain substantial coverage of the electrical apparatus with the liquid coolant whereby the vapors of the coolant may be efficiently evolved to efliciently extract or dissipate the heat from the electrical apparatus. An excellent heat transfer and control of the cooling effect on the vapors evolved is obtained withthe series connected vertical radiator tubes which function to provide progressively increasing cooling surfaces for contact with the vapors.

Since certain changes in the apparatus embodied in the invention described herein may be made without departing from its scope, it is intended that all matter contained in the above description shall be considered as illustrated and not in a limiting sense.

I claim as my invention:

1. In an electrical apparatus, the combination comprising, a sealed casing having an electrical conductor disposed therein, a vaporizable fiuorinated organic liquid coolant within the casing, the liquid coolant boiling between 50 C. and 225 C., a sump for holding a supply of the liquid coolant, means for withdrawing the liquid coolant from the sump and applying a film of the liquid coolant over the electrical conductor whereby cooling of the conductor is efiected mainly by the vaporization of the applied coolantto a condensable vapor, cooling means connected to the casing for receiving evolved vapors therefrom, said cooling means comprising a plurality of cooling devices connected in series with each other, the bottom of the first of the series connected cooling devices being connected to the sealed casing adjacent the upper end thereof, and the bottom of each of the sequential cooling devices of the series being connected to the upper end of the preceding cooling device whereby vapors admitted thereto from the casing -flow upwardly through the cooling devices in succession, the'last of the cooling devices being open to the atmosphere to permit breathing, and a common means connected to the bottom of each of the series connected cooling devices and to thecasing for re turning liquid coolant condensed within the cooling devices to the sump, said common means being below the level of the liquid coolant within the sump whereby the liquid coolant within said common means provides a liquid lock between the cooling devices and the casing.

2. in a transformer, the combination comprising, a sealed casing, having an electrical conductor disposed therein, means for cooling the electrical conductor comprising a vaporizable liquid coolant comprising at least one liquid fluorinated organic compound selected from the group consisting of hydrocarbons, hydrocarbon ethers and tertiary hydrocarbon amines in which at least half the hydrogen atoms have been substituted by at least one halogen selected from the group consisting of fluorine and chlorine, and at least half the halogen is fluorine, the compound having a boiling point of from 50 C. to 225 C. at atmospheric pressure, a sump for holding a supply of the liquid coolant, means for withdrawing the liquid coolant from the sump and applying a film of the liquid coolant over the electrical conductor whereby cooling thereof is efiected mainly by the vaporization of the applied coolant to a condensable vapor, the sump being disposed to receive the excess of the liquid coolant applied to the core and winding, cooling means connected to the casing for receiving evolved vapors therefrom, said cooling means comprising a plurality of vertical cooling devices connected sequentially end to end with each other, the lower end of the first of the sequentially connected vertical cooling devices being connected to the sealed casing adjacent the upper end thereof and the lower end of each of the sequential vertical cooling devices being connected to the upper end of the preceding vertical cooling device whereby vapors admitted thereto from the casing flow upwardly through the cooling devices in succession, the flow of the vapors within the cooling devices being dependent upon the amount of heat generated in the transformer, whereby the cooling effect of the cooling devices on the vapors varies in response to the transformer load, the last of the sequentially connected cooling devices being open to the atmosphere to permit breathing, and a conduit connected to the sealed casing and to the bottom of each of the cooling devices for receiving condensed liquid coolant therefrom, the conduit being disposed below the level of the liquid coolant within the sump so as to maintain a liquid lock between the bottoms of the cooling devices and the casing.

3. In an electrical apparatus, the combination comprising, a sealed casing having an electrical conductor disposed therein, a vaporizable fluorinated organic liquid coolant within the casing, the liquid coolant boiling between 50 C. and 225 C., a sump for holding a supply of the liquid coolant, means for withdrawing the liquid coolant from the sump and applying a film of the liquid coolant over the electrical conductor whereby cooling conductor is effected mainly by the vaporization of the applied coolant to a condensable vapor, cooling means connected to the casing for receiving evolved vapors therefrom, said cooling means comprising a plurality of cooling devices the last of which is open to the atmosphere to permit breathing, eachof the intermediate cooling devices being connected at its top to the bottom of the adjacent cooling device whereby vapors admitted to the cooling means from the casing flow upwardly through the cooling devices in succession, and a common means connected to the bottom of each of the vertical cooling devices and to the sump for returning liquid coolant condensed therein to the sump, said common means being disposed below the level of the liquid coolant within the sump whereby the liquid coolant within said common means provides a liquid lock between the bottoms of the cooling devices and the casing.

4. In an electrical apparatus, the combination comprising, a sealed casing having an electrical conductor disposed therein, a vaporizable fluorinated organic liquid coolant within the casing, the liquid coolant boiling between 50 C. and 225 C., a reservoir in the casing at the lower end thereof for normally containing a supply of the liquid coolant out of contact with the electrical conductor, means for withdrawing the liquid coolant from the reservoir and applying a film of the liquid coolant to the electrical conductor whereby cooling of the conductor is efiected mainly by the vaporization of the applied coolant to a condensable vapor, cooling means connected to the casing for receiving evolved vapors therefrom, said cooling means comprising a plurality of cooling devices connected in series with each other the last of which is open to the atmosphere to permit breathing, the lower end of the first of the series connected cooling devices being connected to the sealed casing adjacent the upper end thereof and the lower end of each of the sequential cooling devices of the series being connected to the upper end of the preceding cooling device whereby vapors admitted thereto from the casing fiow upwardly through the cooling devices in succession, and a common means connected to the lower end of each of the series connected cooling devices and to the casing for returning liquid coolant condensed within the cooling devices to the reservoir, said common means being below the level of the liquid of the coolant within the reservoir whereby the liquid coolant within said common means provides a liquid lock between the lower ends of each of the cooling devices and the casing, said liquid lock between the cooling devices insuring the upward flow of the vapors through the vertical coo-ling devices in succession.

5. In electrical apparatus, in combination, a casing for the electrical apparatus, an electrical conductor disposed in the casing, a vaporizable fluorinated organic liquid coolant boiling between 50 C. and 225 C. for circulation in the casing to dissipate heat from the electrical apparatus, means for circulating the liquid coolant in the casing and applying it to the electrical apparatus whereby when the temperature of the electrical apparatus is above the temperature of vaporization of the liquid coolant the cooling of the electrical apparatus is effected mainly by the conversion of the liquid coolant into a condensable vapor, a plurality of cooling units for condensing the vaporized liquid coolant associated with the casing, the

,. means for condensing the vaporized liquid coolant con taining a gas, a connection for transferring the vaporized liquid coolant from the casing to the cooling units for condensing the vaporized liquid coolant, a return conduit connected to the lower end of each cooling unit for returning the condensed coolant to the casing for further use in the cooling process, said return conduit being adapted to prevent the flow of the vaporized coolant from the casing to the cooling units and from one cooling unit to another through the return conduit, and means for venting during normal operation of the electrical apparatus the gas contained in the means for condensing the vaporized coolant at predetermined pressures.

6. In electrical apparatus, in combination, a casing for the electrical apparatus, an electrical conductor disposed in the casing, a vaporizable fiuorinated organic liquid coolant boiling between 50 C. and 225 C. for circulation in the casing to dissipate heat from the apparatus, means for circulating the liquid coolant in the casing and applying it to the electrical apparatus whereby the cooling of electrical apparatus is effected mainly by the conversion of the liquid coolant into a condensable vapor, means for condensing the vaporized coolant associated with the casing, the means for condensing the vaporized coolant comprising a plurality of radiator devices connected in series with each other, the first of the series connected radiator devices being connected to the casing for transferring the vaporized coolant from the casing to the first of the series connected radiator devices, the last of the series connected radiator devices being open at predetermined pressures to the atmosphere to permit breathing, and a conduit connected to the lower end of each of the series connected radiator devices for returning the condensed coolant from the series connected radiator devices to the casing for further use in the cooling process, said conduit having U-shaped portion between the casing and the first of the series connected radiator devices and between the radiator devices to prevent the flow of the vaporized coolant from the casing to the series connected radiator devices and from one radiator device to another.

7. In electrical apparatus, in combination, a casing for the electrical apparatus, an electrical conductor disposed in the casing, a vaporizable fluorinated organic liquid coolant boiling between 50 C. and 225 C. for circulation in the casing to dissipate heat from the apparatus, means for circulating the liquid coolant in the casing and applying it to the electrical apparatus whereby the cooling of electrical apparatus is elfected mainly by the conversion of the liquid coolant into a condensable vapor, means for condensing the vaporized coolant associated with the casing, the means for condensing the vaporized coolant comprising a plurality of radiator devices connected in series with each other, the bottom portion of the first of the series connected radiator devices being connected to the upper end of the casing for receiving the vaporized coolant from within the casing, and the bottom of each of the sequential radiator devices of the series being connected to the upper portion of the preceding radiator device whereby vapors admitted thereto from the casing flow upwardly through the radiator devices in succession, the last of the series connected radiator devices being open at predetermined pressures to the atmosphere to permit breathing, and another connection for returning the condensed coolant from the series connected radiator devices to the casing for further use in the cooling process, said another connection being adapted to prevent the flow of the vaporized coolant from the casing to the series connected radiator devices.

References Cited in the file of this patent UNITED STATES PATENTS 262,913 Armandy Aug. 22, 1882 478,489 Whitman July 5, 1892 854,276 Darlington May 21, 1907 1,385,827 Hiller July 26, 1921 1,390,386 Rial Sept. 13, 1921 1,641,814 Jones Sept. 6, 1927 1,908,463 Torrance May 9, 1933 2,083,611 Marshall June 15, 1937 2,561,738 Hill July 24, 1951 FOREIGN PATENTS 22,062 Germany Apr. 25, 1883 

5. IN ELECTRICAL APPARATUS, IN COMBINATION, A CASING FOR THE ELECTRICAL APPARATUS, AN ELECTRICAL CONDUCTOR DISPOSED IN THE CASING, A VAPORIZABLE FLUORINATED ORGANIC LIQUID COOLANT BOILING BETWEEN 50*C. AND 225*C. FOR CIRCULATION IN THE CASING TO DISSIPATE HEAT FROM THE ELECTRICAL APPARATUS, MEANS FOR CIRCULATING THE LIQUID COOLANT IN THE CASING AND APPLYING IT TO THE ELECTRICAL APPARATUS WHEREBY WHEN THE TEMPERATURE OF THE ELECTRICAL APPARATUS IS ABOVE THE TEMPERATURE OF VAPORIZATRION OF THE LIQUID COOLANT THE COOLING OF THE ELECTRICAL APPARATUS IS EFFECTED MAINLY BY THE CONVERSION OF THE LIQUID COOLANT INTO A CONDENSABLE VAPOR, A PLURALITY OF COOLING UNITS FOR CONDENSING THE VAPORIZED LIQUID COOLANT ASSOCIATED WITH THE CASING, THE MEANS FOR CONDENSING THE VAPORIZED LIQUID COOLANT CONTAINING A GAS, A CONNECTION FOR TRANSFERRING THE VAPORIZED LIQUID COOLANT FROM THE CASING TO THE COOLING UNITS FOR CONDENSING THE VAPORIZED LIQUID COOLANT, A RETURN CONDUIT CONNECTED TO THE LOWER END OF EACH COOLING UNIT FOR RETURNING THE CONDENSED COOLANT TO THE CASING FOR FURTHER USE IN THE COOLING PROCESS, SAID RETURN CONDUIT BEING ADAPTED TO PREVENT THE FLOW OF THE VAPORIZED COOLANT FROM THE CASING TO THE COOLING UNITS AND FROM ONE COOLING UNIT TO ANOTHER THROUGH THE RETURN CONDUIT, AND MEANS FOR VENTING DURING NORMAL OPERATION OF THE ELECTRICAL APPARATUS THE GAS CONTAINED IN THE MEANS FOR CONDENSING THE VAPORIZED COOLANT AT PREDETERMINED PRESSURES. 